For a product that’s been made for millennia, it’s quite incredible that beer brewing techniques – extract sugar from grains, flavour with hops and ferment – have barely changed.
But while brewers might now have snazzier equipment, specialty yeasts and a whole realm of food science behind them, the process guzzles energy.
Large breweries might use 32 kilowatt hours to produce 100 litres of beer (for comparison, the average Australian home uses 18 kilowatt hours each day) and for small and craft breweries, that number is higher. And between four and 11 litres of wastewater is churned out for each litre of beer.
A technique developed by Lorenzo Albanese and some lucky colleagues at at the Institute of Biometeorology in Florence, Italy, and published on the online repository Arxiv, decreases both.
The process, called cavitation, harnesses the power of bubbles – not the carbonated kind, but tiny spheres that can generate huge temperatures and pressures which change the structure of beer components on a molecular level.
It uses about a third less energy and needs less cleaning – so less water.
And the all-important taste test gets a tick too, with the brews retaining their flavour and foamy head.
So how does this new-fangled gadget work?
The apparatus is fairly simple. A pipe leading from a cylindrical vessel, which contains grains and water, channels water to a pump.
The pump pushes the water into what’s called the cavitation reactor. It is, in essence, a propeller, and it’s where the bubbles are produced.
The propeller spins at around 2,900 revolutions per minute, perhaps a little faster than a blender’s lowest setting.
As the tips of the propeller drags through the liquid, they create low-pressure whirls that bloom into bubbles, which are then jetted into the cylindrical vessel.
But after a split second, the overwhelming pressure of all the liquid crushes them again. This is cavitation.
You can see the same effect on ship propellers and, of course, in the natural world.
Only a few centimetres long, snapping shrimp generate the crackling sound you hear if you put your head underwater in the sea.
They have one massive claw which snap shut at immense speeds. The sound is not produced when the two halves of the claw clamp together, but by the water jet that’s forced out from between them.
As the high-velocity water stream is moving super fast compared to its surrounds, its pressure drops – creating bubbles.
The vigorous push-pull exerted by the short-lived bubbles can heat liquids hundreds of degrees and increase pressure thousands of times.
So it’s no wonder cavitation techniques have been in processes such as water treatment and pasteurisation, killing off nasties, since the 1990s.
Previous work showed pumping ultrasound through liquids can increase the rate at which molecules, such as carbohydrates, leak out of a cell. This is because a cell’s wall or membrane is jostled by the bubbly onslaught, momentarily opening doors for stuff to leak out.
Albanese and his crew thought cavitation might trim a big part of the brewing process – namely, scraping as much starch out of grain as possible – and what better way to do it than try it in their own microbrewery?
So they tried a few recipes in modified equipment with 230-litre capacity. After undergoing cavitation, they continued as you usually would – added hops, fermented and bottled.
The injected bubbles pulverised the grain, reduced it to fragments just100 microns (0.1 millimetre) in size after a few minutes. This huge surface area meant all but a few traces of starch was extracted. The bubbles also shook out foul-tasting volatile compounds.
Now, the nitty gritty. With their new design, energy savings exceeded 30%. It could, they write, run on solar thermal and photovoltaic power.
Cleaning and sanitising the equipment is largely unnecessary, too, meaning less water needed.
While it sounds great, there’s a caveat or two (of course).
The researchers only made pales and pilsners. There’s no reason to think the technique wouldn’t work on other types of beer, but that’s not shown in their paper.
The big one, though, is the gear. The equipment Albanese and co used is commercially available, but the cavitation is extremely corrosive – think of those extreme temperatures and pressures.
In fact, ships’ propellers aren’t immune from this either, and can end up with cavitation corrosion. Whether stainless steel gear can go the distance in a brewery over long periods is another thing entirely.
But for a process that’s barely changed over the millennia, it’s an intriguing thought. And the researchers bottled roughly 500 litres of beer from their experiment – not a bad way to do science.
Belinda Smith is a science and technology journalist in Melbourne, Australia.
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